What did the "rightly guided" caliphs use as guides to leadership?

The principle guiding force that the caliphs used to guide their leadership was the Koran or Qur'an and Mohammad's actions. Muslims believe this book was dictated to Mohammad through Gabriel from God. Through the text, the caliphs justified Jihad, or struggling for the path of God, which allowed the justification for the expansion of Islam during the time through peace and force.